Due to the ever increasing amount of ongoing research in the biological and medical arenas, there is a vast need for readily available biological materials in which not only the structural integrity, but also the cellular/biological integrity, of the biological materials is preserved so that such materials can be used by biological and medical diagnosticians/researchers for extended periods after the preservation of these materials. Such materials are very important in carrying out research for medical purposes such as cancer research, Alzheimer's research, etc and also as part of the diagnosis of specific diseases as well as following the advancement or prognosis of such diseases. As a result of this need, there is an ongoing increase in the demand for a process that will not only decrease, but also possibly prevent, over time, the degradation of the structural aspects of the biological materials as well as the genetic integrity of such materials. More specifically, in the biological and medical fields, it is desirable to have biological materials (for example, the DNA, RNA and proteins) which have undergone very limited, if any, degradation of the cellular components of the biological materials over a period of time. Such preservation processes would allow further analysis of specific biological materials at a later date or would allow such biological materials to be used at a later date in additional tests or studies.
While in the living host, there are mechanisms which allow for the repair of cellular components such as DNA, RNA and proteins. However, once the tissue is excised or separated from the living host, this repair ceases and the cellular components begin to rapidly break down. A variety of prior art processes are available that allow for the preservation of human and/or animal tissue, including at the individual cellular level. For example, tissue such as biopsies are typically stored as formaldehyde-fixed paraffin-embedded samples (FFPE) thereby allowing for histopathological examination of the preserved sample. FFPE's are prepared by dipping a sample in a formaldehyde solution for a period of time—in recent years using a formaldehyde solution buffered to pH 7.0—followed by embedding the sample in paraffin for storage.
In addition, a variety of methods have been proposed for addressing the issue of nucleic acid preservation from degradation. One of these methods as disclosed in U.S. Pat. No. 6,204,375 involves using specific chemicals and/or chemical reagents such as sulfate salts, while another method as disclosed in U.S. Pat. No. 7,138,226 involves the use of non-aqueous composition of 5-20% polyethylene glycol and 80-95% methanol. Other methods of bio-molecule preservation include inhibition of RNA degrading enzymes such as ribonucleases as disclosed in U.S. Pat. No. 6,777,210 and biological proteases as disclosed in U.S. Pat. No. 3,682,776. Cryo-preservation using ultra low temperatures alone or in combination with chemical solutions has also been demonstrated to be an effective means of preserving bio-molecules in a frozen state as disclosed in Japanese Patent No. 59082301, U.S. Pat. Nos. 4,423,600 and 5,328,821.
The use of inert gases for organ preservation under ultra-hyperbaric pressure and ultra low temperatures has also been described in U.S. Pat. No. 3,677,024. Oxygenation of living tissue is disclosed in U.S. Pat. No. 5,362,622. Using oxygen and/or oxygen containing gas mixtures in the presence of a circulating nutrient is another method wherein gases and/or gas mixtures have been used for organ and tissue preservation as disclosed in U.S. Pat. No. 3,772,153.
Even with these various processes, there still exists a need for a process in which the deformation of cellular components and fragmentation of bio-molecules such as RNA, DNA and proteins are minimized or completely eliminated since such materials are not adequate for use in diagnostic and prognostic processes as well as currently available research applications. Many prior art processes prove to be less than desirable when preserving biological materials for extended periods of time due to damage to the biological materials caused by the actual preservation process utilized. Depending upon the conditions of preservation and/or storage, the biological materials may tend to degrade more rapidly than normal and to the degree that they cannot successfully be used for biological/medical research purposes. As time progresses, materials preserved in such manners are typically less and less acceptable for their intended purpose due to structural breakdown of the sample as well as the breakdown of cellular components such as DNA, RNA and proteins. Accordingly, there is a need for a process for preserving biological materials which not only slows down or eliminates the degradation of the structural integrity of biological materials but also minimizes or eliminates the degree of degradation of cellular components such as DNA, RNA and proteins.